Electrophysiology device with electrodes having increased surface area

ABSTRACT

A medical device includes a body and at least one electrode disposed thereon. The electrode includes a metallic substrate, such as a platinum group metal, an alloy of platinum group metals, or gold. The surface of the substrate is modified in a manner that increases its effective surface area without inducing bulk heating. For example, the surface of the substrate can be laser textured and/or coated, such as with titanium nitride or iridium oxide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Ser.No. 62/591,656, filed 28 Nov. 2017, which is hereby incorporated byreference as though fully set forth herein.

BACKGROUND

The instant disclosure relates to catheters for use in medicalprocedures, such as electrophysiology studies. In particular, theinstant disclosure relates to electrophysiology catheters that includeelectrodes with increased surface area and decreased impedance.

Catheters are used for an ever-growing number of procedures, such asdiagnostic, therapeutic, and ablative procedures, to name just a fewexamples. Typically, the catheter is manipulated through the patient'svasculature and to the intended site, for example, a site within thepatient's heart.

A typical electrophysiology catheter includes an elongate shaft and oneor more electrodes on the distal end of the shaft. The electrodes may beused for ablation, diagnosis, or the like. Oftentimes, these electrodesinclude ring electrodes that extend about the entire circumference ofthe catheter shaft, as well as a tip electrode.

As the dimensions of a measurement electrode decrease, the complex ACimpedance with respect to a counter-electrode will generally increase.The increased impedance associated with smaller measurement electrodescan have undesirable effects during electrophysiology studies, such aselectroanatomical mapping.

There are two primary contributing factors to the increased impedance. Afirst contributing factor is related to the dimensional dependence ofthe volumetric resistance (i.e., smaller electrodes have regions ofhigher current density). A second contributing factor is related to thecapacitance of the electrode (i.e., as electrode dimensions shrink, theionic AC current can become limited by how much charge can build up atthe electrode surface). The second contributing factor, therefore,depends upon the total microscopic surface area of the electrode versusthe macroscopic dimensional surface area of the electrode.

BRIEF SUMMARY

Disclosed herein is a method of manufacturing a medical device,including: forming a medical device body; forming at least one electrodeaccording to a process including: forming a metallic substrate; andtreating a surface of the metallic substrate in a manner that increasesan area of the surface of the metallic substrate and that reduces thereal component of impedance (resistance) of the metallic substrate whenoperating at a frequency within a cardiac medical range (e.g., less thanabout 20 kHz); and securing the at least one electrode to the medicaldevice body. The metallic substrate can be selected from the groupconsisting of gold, platinum group metals (e.g., ruthenium, rhodium,palladium, osmium, iridium, and platinum), and alloys of platinum groupmetals (e.g., platinum-iridium alloy).

In aspects of the disclosure, the surface of the metallic substrate istreated by applying laser energy to the surface of the metallicsubstrate, for example using a femtosecond laser, thereby texturing thesurface of the metallic substrate. In other aspects of the disclosure,the surface of the metallic substrate can be treated by applying acoating, such as titanium nitride, iridium oxide, platinum, platinumiridium, and/or an electro-conductive polymer coating thereto. Thecoating may be applied by chemical vapor deposition, physical vapordeposition, or electrochemical deposition. In still other aspects of thedisclosure, the surface of the metallic substrate is both laser-texturedand coated, with the treatments occurring in either order.

Also disclosed herein is a medical device, such as a multi-electrodeelectrophysiology catheter, formed according to a process, including thesteps of: forming a medical device body; forming at least one electrodeaccording to a process including: forming a metallic substrate; andtreating a surface of the metallic substrate in a manner that increasesan area of the surface of the metallic substrate and that reduces theresistance of the metallic substrate when operating at a frequencywithin a cardiac medical range (e.g., less than about 20 kHz); andsecuring the at least one electrode to the medical device body. Thecoating may be applied by chemical vapor deposition, physical vapordeposition, or electrochemical deposition. The metallic substrate can beselected from the group consisting of gold, platinum group metals, andalloys of platinum group metals.

In aspects of the disclosure, the surface of the metallic substrate istreated by applying laser energy to the surface of the metallicsubstrate, for example using a femtosecond laser, thereby texturing thesurface of the metallic substrate. In other aspects of the disclosure,the surface of the metallic substrate can be treated by applying acoating, such as titanium nitride, iridium oxide, platinum, platinumiridium, and/or an electro-conductive polymer coating thereto. In stillother aspects of the disclosure, the surface of the metallic substrateis both laser-textured and coated, with the treatments occurring ineither order.

Also disclosed herein is a medical device including: a body; and atleast one electrode disposed on the body, wherein the at least oneelectrode includes a metallic substrate. A surface of the substrate ismodified in a manner that increases its effective surface area withoutinducing bulk heating and with a reduction in resistance of the metallicsubstrate when operating at a frequency within a cardiac medical range(e.g., less than about 20 kHz). For example, the surface of thesubstrate can be laser textured and/or coated.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts an electrophysiology catheter andassociated systems.

FIG. 2 is a close-up view of the distal region of the catheter shown inFIG. 1 .

FIGS. 3A-3C are schematic illustrations of exemplary textured electrodesurfaces according to aspects of the instant disclosure.

DETAILED DESCRIPTION

For purposes of illustration, the present teachings will be described inconnection with a multi-electrode mapping and ablation catheter 10, suchas illustrated in FIG. 1 . As shown in FIG. 1 , catheter 10 generallyincludes an elongate catheter body 12 having a distal region 14 and aproximal end 16. A handle 18 is shown coupled to proximal end 16. FIG. 1also shows connectors 20. Connectors 20 are configured to be connectedto a source of ablation energy (schematically illustrated as RF source22, which can be, for example, the Ampere™ RF ablation generator ofAbbott Laboratories, Abbott Park, Ill.), an electrophysiology mappingdevice or system (schematically illustrated as 24, which can be, forexample, the EnSite Precision™ cardiac mapping system, also of AbbottLaboratories), and a programmable electrical stimulator (schematicallyillustrated as 25, which can be, for example the EP-4™ cardiacstimulator, also of Abbott Laboratories). Although FIG. 1 depicts threeseparate connectors 20, it is within the scope of the instant disclosureto have a combined connector 20 that is configured for connection to twoor more of RF source 22, electrophysiology mapping device 24, andprogrammable electrical stimulator 25.

Various additional aspects of the construction of catheter 10 will befamiliar to those of ordinary skill in the art. For example, the personof ordinary skill in the art will recognize that catheter 10 can be madesteerable, for example by incorporating an actuator into handle 18 thatis coupled to one or more steering wires that extend through elongatecatheter body 12 and that terminate in one or more pull rings withindistal region 14. Likewise, the ordinarily skilled artisan willappreciate that catheter 10 can be an irrigated catheter, such that itcan also be coupled to a suitable supply of irrigation fluid and/or anirrigation pump. As a further example, those of ordinary skill in theart will appreciate that catheter 10 can be equipped with force feedbackcapabilities.

Insofar as such features are not necessary to an understanding of theinstant disclosure, they are neither illustrated in the drawings norexplained in detail herein. By way of example only, however, catheter 10can incorporate various aspects and features of the following catheters,all from Abbott Laboratories: the EnSite™ Array™ catheter; theFlexAbility™ ablation catheter; the Safire™ BLU™ ablation catheter; theTherapy™ Cool Path™ irrigated ablation catheter; the Livewire™ TCablation catheter; and the TactiCath™ Quartz irrigated ablationcatheter.

FIG. 2 is a close-up of distal region 14 of catheter 10. Distal region14 of catheter 10 includes a tip electrode 26 positioned at its distalend and a plurality of additional electrodes 28 proximal of tipelectrode 26. In particular, FIG. 2 depicts five ring electrodes 28. Theperson of ordinary skill in the art will understand and appreciate,however, that by varying the size (e.g., width) and spacing ofelectrodes 28, different diagnostic and/or therapeutic objectives and/oroutcomes can be achieved. For example, the ordinarily skilled artisanwill appreciate that, as electrodes 28 become smaller and closertogether, the electrograms collected thereby will become sharper andmore localized evidencing better depiction of local, near-fielddepolarization of the cardiac tissue in contact with the electrodes.Thus, it should be understood that distal region 14 can include anynumber of such electrodes 28 (e.g., 9 electrodes 28 for a decapolarcatheter 10) and that the inter-electrode spacing can vary along thelength of distal region 14.

Electrodes 28 may include any metal capable of detecting and conductingthe local electrical signal. Suitable materials for electrodes 28include, without limitation, platinum group metals (e.g., platinum,palladium, rhodium, osmium, ruthenium, iridium), alloys of platinumgroup metals (e.g., platinum-iridium alloys), and gold. In otherembodiments of the disclosure, electrodes 28 include multiple layers ofconductive materials, such as gold-coated copper.

Electrodes 28 can also be of various physical configurations. Theseinclude, by way of example only, ring electrodes, segmented ringelectrodes, partial ring electrodes, flexible circuit electrodes,balloon electrodes, and spot electrodes. Various configurations ofelectrodes 28 (as well as electrode 26) are disclosed in InternationalPublication No. WO 2016/182876, which is hereby incorporated byreference as though fully set forth herein.

The instant disclosure provides electrodes having increased microscopicsurface areas (that is, electrodes with surface areas exceeding those ofplanar electrodes having the same or similar dimensions). According toaspects of the disclosure, the increased microscopic surface area isachieved by treating a surface 30 of the electrode substrate 32 as shownin FIGS. 3A-3C. It is further desirable that the treatment increase themicroscopic surface area of the electrode without causing bulk heating.

Electrodes having increased microscopic surface areas can be employed togood advantage in various electrophysiology devices including, withoutlimitation, electrophysiology mapping catheters (e.g., basket catheters,HD grid catheters) and ablation catheters. The basic structure of suchdevices will be familiar to those of ordinary skill in the art, and arealso illustrated in, inter alia, international application no.PCT/US2018/046953, United States patent application publication no.2017/0112405, and U.S. Pat. No. 8,560,086, all of which are herebyincorporated by reference as though fully set forth herein. It should beunderstood, however, that the foregoing are merely representative ofcertain types of electrophysiology devices that can include electrodesaccording to the instant teachings; insofar as electrodes according tothe instant disclosure can be employed to good advantage in othercontexts, the foregoing list of electrophysiology devices should not beregarded as exclusive, exhaustive, or otherwise limiting.

In embodiments of the disclosure, surface 30 of electrode substrate 32is treated by applying laser energy thereto, for example by using afemtosecond laser, to create a textured surface 30 on electrodesubstrate 32. FIGS. 3A through 3C illustrate three exemplary texturedsurfaces 30. The textured surface 30 of FIG. 3A has uniform peaks andvalleys extending in a single dimension; the textured surface 30 of FIG.3B has varying peaks and valleys extending in a single dimension; andthe textured surface 30 of FIG. 3C has varying peaks and valleysextending in two dimensions. Of course, other patterns of texturedsurface 30 are contemplated and regarded as within the scope of theinstant disclosure.

In general, the real component of the overall measured impedance (thatis, the resistance) will have an interfacial component that is affectedby the local ionic concentration, which results in a frequencydependency of the measured resistance. In aspects of the instantdisclosure, therefore, it can be desirable for textured surface 30 tohave a length scale comparable to the ionic double layer thickness(e.g., nanoscaled surfaces).

In other embodiments of the disclosure, surface 30 of electrodesubstrate 32 is treated by applying a coating thereto, such as atitanium nitride, iridium oxide, platinum, and platinum-iridiumcoatings. In other embodiments, the coating is a durableelectro-conductive polymer coating, such as Amplicoat™ (Heraeus MedicalComponents LLC, Yardley, Pa.). The coating may be applied to substrate32 by physical vapor deposition, chemical vapor deposition,electrochemical deposition, or the like.

In still further embodiments of the disclosure, surface 30 of electrodesubstrate 32 is treated both by applying laser energy thereto and byapplying a coating thereto. These treatments can be carried out ineither order.

In general, the amount of impedance reduction relative to a planarelectrode of the same or similar dimensions that results from theforegoing treatments can depend upon factors such as electrodedimensions, signal magnitude, signal frequency, and media ionicstrength. As one example, at operating frequencies within the cardiacmedical range (e.g., less than about 20 kHz), and measured relative to aplanar electrode having a surface area of about 1 mm², treatmentsaccording to the instant teachings can yield impedance improvements(that is, reductions) of at least about 20%. It should also beunderstood that the percentage impedance improvement increases as thecomparable planar electrode surface area decreases. Thus, in certainembodiments, the treatments disclosed herein can yield impedanceimprovements (that is, reductions) of at least about 30%, and, in someinstances, of at least about 40%.

Although several embodiments have been described above with a certaindegree of particularity, those skilled in the art could make numerousalterations to the disclosed embodiments without departing from thespirit or scope of this disclosure.

For example, the electrodes described herein can not only be formedprior to being attached to the body of a medical device (e.g., anelectrophysiology catheter), but can also be formed following attachmentto the body of the medical device.

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other.

It is intended that all matter contained in the above description orshown in the accompanying drawings shall be interpreted as illustrativeonly and not limiting. Changes in detail or structure may be madewithout departing from the spirit of the invention as defined in theappended claims.

What is claimed is:
 1. A method of manufacturing a medical device,comprising: forming a medical device body; forming at least oneelectrode according to a process comprising: forming a metallicsubstrate; and treating a surface of the metallic substrate in a mannerthat increases an area of the surface of the metallic substrate and thatreduces resistance of the metallic substrate when operating at afrequency within a cardiac medical range; and securing the at least oneelectrode to the medical device body, wherein the step of treating thesurface of the metallic substrate forms a plurality of peaks and valleysextending uniformly along at least one dimension upon the surface of themetallic substrate.
 2. The method according to claim 1, wherein themetallic substrate is selected from the group consisting of gold,platinum group metals, and alloys of platinum group metals.
 3. Themethod according to claim 1, wherein treating a surface of the metallicsubstrate in a manner that increases an area of the surface of themetallic substrate comprises applying a coating to the surface of themetallic substrate.
 4. The method according to claim 3, wherein applyinga coating to the surface of the metallic substrate comprises depositingthe coating on the metallic substrate via chemical vapor deposition. 5.The method according to claim 3, wherein applying a coating to thesurface of the metallic substrate comprises depositing the coating onthe metallic substrate via physical vapor deposition.
 6. The methodaccording to claim 3, wherein applying a coating to the surface of themetallic substrate comprises depositing the coating on the metallicsubstrate via electrochemical deposition.
 7. The method according toclaim 3, wherein the coating comprises at least one of titanium nitride,iridium oxide, platinum, and platinum iridium.
 8. The method accordingto claim 3, wherein the coating comprises an electro-conductive polymercoating.
 9. A medical device formed according to a process comprising:forming a medical device body; forming at least one electrode accordingto a process comprising: forming a metallic substrate; and treating asurface of the metallic substrate in a manner that increases an area ofthe surface of the metallic substrate and that reduces resistance of themetallic substrate when operating at a frequency within a cardiacmedical range; and securing the at least one electrode to the medicaldevice body, wherein the step of treating the surface of the metallicsubstrate forms a plurality of peaks and valleys extending uniformlyalong at least one dimension upon the surface of the metallic substrate.10. The medical device according to claim 9, wherein the metallicsubstrate is selected from the group consisting of gold, platinum groupmetals, and alloys of platinum group metals.
 11. The medical deviceaccording to claim 9, wherein treating a surface of the metallicsubstrate in a manner that increases an area of the surface of themetallic substrate comprises applying a coating to the surface of themetallic substrate.
 12. The medical device according to claim 11,wherein the coating comprises at least one of titanium nitride andiridium oxide.
 13. The medical device according to claim 11, wherein thecoating comprises an electro-conductive polymer coating.
 14. The medicaldevice according to claim 9, wherein the medical device comprises amulti-electrode electrophysiology catheter.
 15. A medical devicecomprising: a body; and at least one electrode disposed on the body,wherein the at least one electrode includes a metallic substrate, andwherein a surface of the substrate is modified in a manner thatincreases its effective surface area without inducing bulk heating andwith a reduction in resistance of the metallic substrate when operatingat a frequency within a cardiac medical range, and wherein the manner ofmodifying the surface of the substrate forms a plurality of peaks andvalleys extending uniformly along at least one dimension of the surfaceof the metallic substrate.
 16. The medical device according to claim 15,wherein the surface of the substrate is coated.
 17. The method accordingto claim 1, wherein the plurality of peaks and valleys extend uniformlyalong two dimensions of the surface of the metallic substrate.
 18. Themethod according to claim 1, wherein the plurality of peaks extend abovethe surface of the metallic substrate by less than an amount equivalentto an ionic double layer thickness of an electrolyte employed during useof the medical device.
 19. The method according to claim 1, wherein theplurality of peaks extend above the surface of the metallic substrate byless than 100 nanometers.